1. Field
The present invention relates generally to data communication, and more specifically to a novel and improved method and apparatus for processing data for transmission in a wireless communication system using selective channel inversion.
2. Background
A multi-channel communication system is often deployed to provide increased transmission capacity for various types of communication such as voice, data, and so on. Such a multi-channel system may be a multiple-input multiple-output (MIMO) communication system, an orthogonal frequency division modulation (OFDM) system, a MIMO system that utilizes OFDM, or some other type of system. A MIMO system employs multiple transmit antennas and multiple receive antennas to exploit spatial diversity to support a number of spatial subchannels, each of which may be used to transmit data. An OFDM system effectively partitions the operating frequency band into a number of frequency subchannels (or frequency bins), each of which is associated with a respective subcarrier on which data may be modulated. A multi-channel communication system thus supports a number of “transmission” channels, each of which may correspond to a spatial subchannel in a MIMO system, a frequency subchannel in an OFDM system, or a spatial subchannel of a frequency subchannel in a MIMO system that utilizes OFDM.
The transmission channels of a multi-channel communication system typically experience different link conditions (e.g., due to different fading and multipath effects) and may achieve different signal-to-noise-plus-interference ratios (SNRs). Consequently, the transmission capacities (i.e., the information bit rates) that may be supported by the transmission channels for a particular level of performance may be different from channel to channel. Moreover, the link conditions typically vary over time. As a result, the bit rates supported by the transmission channels also vary with time.
The different transmission capacities of the transmission channels plus the time-variant nature of these capacities make it challenging to provide an effective coding and modulation scheme capable of processing data prior to transmission on the channels. Moreover, for practical considerations, the coding and modulation scheme should be simple to implement and utilize at both the transmitter and receiver systems.
There is therefore a need in the art for techniques to effectively and efficiently process data for transmission on multiple transmission channels with different capacities.